1. Field of the Invention
The invention relates to distillate fuel compositions of reduced nickel corrosivity containing additives.
2. Description of the Related Art
Acidic sulfur species such as sulfonic acids, alkyl sulfate esters and sulfuric acid contained in hydrocarbon streams are corrosive and damaging to metal equipment, particularly nickel and nickel alloys such as Monel (70% Ni/30% Cu). Acidic sulfur compounds may be present in varying concentrations in refined fuel products that comprise in whole or in part alkylate product. Alkylate product may sometimes contain small amount of corrosive sulfur compounds. The compounds are usually alkyl sulfate esters formed by the addition of sulfuric acid to the olefin in the alkylation process. These resulting esters can hydrolyzed in the presence of heat and water to sulfuric acid and alcohol. Formation of these alkyl esters is inherent in the alkylation mechanism; however, under proper operating conditions the reaction is of only minor importance. The sulfuric acid resulting from the decomposition of even these minor concentrations of esters has a particularly corrosive effect on equipment such as nickel director in engine injection system, nickel parts in in-tank fuel pump in motor vehicles, etc.
Corrosion of silver, copper and copper alloy by elemental sulfur in fuels is controlled by use of additives. These additives are either sulfur scavengers or metal deactivators that coat metal surfaces thus preventing attack of the surface by sulfur or sulfur species.
Up to now, however, no commercial corrosion inhibitors were known that were suitable for preventing corrosion of nickel from acidic sulfurous species such as sulfuric acid, sulfurous acid or alkyl sulfate esters. Nickel parts are common in internal combustion engines and in the fuel systems for such engines.
U.S. Pat. No. 3,663,561 discloses useful 5-mercapto-2-hydrocarbyldithio-1,3,4-thiadiazoles and their preparation thereof. This type of compound is well known to have the ability to inhibit corrosion of copper, brass and silver metal parts from elemental sulfur. The commercially available Elco 461, a 2,5-(bis)-(hydrocarbyldithio-1,3,4-thiadiazole, Hitec 4313, Hitec 4312 and Tolad 9717 fall in this category.
U.S. Pat. No. 5,035,720 discloses oil soluble adducts of a triazole and a basic nitrogen compound (an amine) which are useful for inhibiting corrosion of copper and aluminum surfaces in fuel systems, and more particularly to such compositions and methods for inhibiting corrosion of copper and aluminum surfaces in petroleum-based fuel systems which contain elemental sulfur or sulfur-containing compounds, such as mercaptans. The triazole is benzotriazole or tolyltriazole. The amine is water-insoluble such as alkoxyamine with 2-15 alkoxy groups. The adduct is obtaining from tolyltriazole and bis (hydroxyethyl) cocoamine, bis (hydroxyethyl) octadecylamine, bis (hydroxyethyl)-2-ethylhexyl-amine or bis (hydroxyethyl) oleylamine.
U.S. Pat. No. 5,653,787 relates to an additive composition for reducing silver corrosion in two-cycle engines running on gasoline containing elemental sulfur contaminant, the additive comprising a 2,5-dihydrocarbyldithio- 1,3,4-thiadiazole in combination with an adduct of benzotriazole or tolyltriazole with an alkoxyamine.
U.S. Pat. No. 4,871,465 discloses lubricating oils that contain a silver protective agent comprising: (a) a sulfurized olefin, sulfurized fatty acid, sulfurized hydroxyaromatic compound, sulfur heterocyclic compound, organic sulphide or dithiocarbamate, or (b) a product obtained by reacting a saturated aliphatic hydrocarbon-substituted dicarboxylic acid with a 1-15 carbon hydrocarbyl substituted aminoguanidine. The combination of (a) and (b) have a synergistic affect in reducing wear of silver bearings and avoid the environmental problems associated with chlorinated hydrocarbons. The oils are especially suitable for use in medium-speed diesel engines such as are used in railway locomotives, marine tugs and stationary power units.
U.S. Pat. No. 5,141,675 discloses a method for inhibiting the corrosion of metallic surfaces, particularly copper/nickel alloy surfaces in contact with aqueous system, comprising adding to the aqueous system being treated an effective amount of a polyphosphate in combination with an alkyl or alkoxy benzotriazole, tolytriazole or mercaptobenzothiazole derivative.
U.S. Pat. No. 4,464,276 discloses the combination of (di) amine adducts of benzotriazoles with overbased sulfurized calcium alkylphenolate. The additives mixture is useful as antioxidant and corrosion inhibitor in medium speed diesel lubricant compositions. There is no mention of the use of 2,5-hydrocarbyldithio-1,3,4-thiadiazole.
U.S. Pat. No. 5,143,634 discloses a lube composition encompassing (i) Mannich reaction product of benzotriazole, amine and formaldehyde, (ii) sulfur-containing compound, and (iii) metallic detergent.